Ultrasonic welding uses high frequency vibrations to weld two or more work pieces. This process has applications in the electronic, automotive, aerospace, appliance, and medical industries, for example, and is commonly used for metals and plastics.
The process of ultrasonic welding and the equipment and systems to perform the same are generally known. In reference to FIG. 1, a generic ultrasonic welding system 10 is shown. The system 10 shown in FIG. 1 is configured to weld two wires 22, 24 using ultrasonic vibrations. The system 10 includes an anvil 20. An end of a first wire 22 and an end of a second wire 24 are positioned in an overlapping manner on a surface of the anvil 20. The system 10 includes a stack 30 for transferring energy in the form of ultrasonic vibrations to the ends of the two wires 22, 24 to form the weld. The stack 30 includes a converter 32 for converting electric power into mechanical vibrations, a booster 34 for optionally modifying the amplitude of the vibrations generated by the convertor 32, and a horn 36 for applying the vibrations to the ends of the wires 22, 24. A power supply 40 delivers a high power AC signal to the convertor 32. A controller 50 controls and monitors the system 10.
During operation of the ultrasonic welding system 10, a force is applied to the stack 30, thereby compressing the ends of the two wires 22, 24 between the horn 36 and the anvil 20. The power supply 40 is actuated via the controller 50 to provide power to the convertor 32, creating a high frequency vibration. The vibration is transmitted through the booster 34, which may amplify the vibration. The vibration is then transmitted to the horn 36 which applies it to the ends of the two wires 22, 24 thereby welding them together.
A disadvantage of such systems is that if insufficient energy is transmitted to the parts being welded via the vibrations of the horn, it can result in an inferior weld that does not meet established criteria for a desired application.
Another disadvantage of such systems is that any defect with the power supply or the stack can result in insufficient energy being used to form the weld, resulting in a substandard weld. In some cases, the poor quality of the weld is evident upon inspection and the part is discarded. Nevertheless, if a substandard weld is discovered, an inspection of the welding system should be performed to determine the reason for the substandard weld.
A disadvantage with diagnosing such systems is that it is difficult to determine whether the substandard weld is a result of a problem with the power supply, the stack, or both. This disadvantage can result in significant, and costly, downtime to diagnose and correct the problem. The stack is typically a complex and precise instrument and, therefore, it is time consuming and difficult to identify and correct errors associated therewith. As a result, there is a tendency to attribute poor quality welds to errors with the power source instead of the stack, even when the power source is operating according the specification. This can result in incurring unnecessary costs to repair or replace the power source.
Another disadvantage of such ultrasonic welding systems is that in some cases, a problem with the stack results in a substandard weld, albeit one that is not perceptible to operator of the system. In such circumstances, the substandard weld may be discovered in a subsequent quality control check. In such cases, an entire lot of welded work pieces may be discarded. In other circumstances, the substandard weld may not be identified.
It is an object of the present invention to overcome these disadvantages and other disadvantages associated with the prior art.